Within the framework of an airport navigation function (which makes it possible to display on a screen of the flight deck of an aircraft an airport map on which the current position of the aircraft is indicated), it is necessary to ascertain the exact position of the aircraft when it is situated on the ground. The accuracy and the rate of refreshing of this position are decisive parameters for ensuring the credibility of the information displayed, with respect to the exterior markers visible by the pilot of the aircraft. The availability of this position, together with the appropriate performance, must be guaranteed for all the airport surfaces capable of receiving aircraft equipped with such a device, thereby assuming that the position is determined without relying solely on the use of possible equipment available on the ground to improve the calculation, given that such equipment is not envisaged on all airports.
To determine the position of the aircraft, use is generally made of a reception assembly which is associated with a satellite positioning system, in particular of GPS type (“Global Positioning System”), for example Navstar, Galileo, GNSS, GLONASS. This reception assembly comprises in a standard manner a reception antenna which is mounted on the roof of the aircraft, as well as a receiver which is linked to this antenna and which generates aircraft position data, on the basis of signals detected by said antenna. However, such a positioning assembly delivers the position data, that is to say information about the position of the aircraft, for in-flight navigation requirements only once a second, this being insufficient for airport navigation requirements, since such a delivery frequency does not make it possible to retrieve the displacements of the aircraft in a satisfactory manner.